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IC 8957 



Bureau of Mines Information Circular/1983 




Dust Sources and Controls on the Six 
U.S. Longwall Faces Having the Most 
Difficulty Complying With Dust 
Standards 

By Robert A. Jankowski and John A. Organiscak 




UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 8957 

Dust Sources and Controls on the Six 
U.S. Longwall Faces Having the Most 
Difficulty Complying With Dust 
Standards 

By Robert A. Jankowski and John A. Organiscak 




UNITED STATES DEPARTMENT OF THE INTERIOR 
James G. Watt, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 




4> 



^ <P$> 



<\6 



c c 



Library of Congress Cataloging in Publication Data: 



Jankowski, Robert A 

Dust sources and controls on the six U.S. longwall faces having the 
most difficulty complying with dust standards. 

(Bureau of Mines information circular ; 8957) 

Bibliography: p. 12-13. 

Supt. of Docs, no.: I 28.27:8957. 

1. Coal mines and mining— United States— Dust control. 2. Coal 
mines and mining— Dust control— Standards— United States. I. Organis- 
cak, John A. II. Title. III. Series: Information circular (United States. 
Bureau of Mines) ; 8957. 



-TN2t5rU4— ~ [TN312] 622s [622'. 8] 83-14228 



CONTENTS 

Page 

Abstract 1 

Introduction 2 

Identification of dust sources 2 

Effectiveness of existing controls 3 

Cutting sequence design 3 

External water spray system 4 

Shearer water supply 6 

Stage loader and coal transport 8 

Support dust 9 

Total approach required 11 

Conclusions 12 

References 12 

Appendix A. — Sampling procedures and data analysis for dust source 

determinations 14 

Appendix B. — Sampling procedures for evaluating dust control effectiveness 

using instantaneous instruments 18 

ILLUSTRATIONS 



1. 
2. 
3. 
4. 
5. 
6. 
7. 
8. 
9. 

B-l. 
B-2. 



1. 

2. 
A-l. 
A-2. 
A-3. 
A-4. 
A-5. 
A-6. 



Comparison of dust level profiles around the shearer at mines D and F.., 

Dust level profile around the shearer at mine B , 

Dust level profile around the shearer at mine E , 

Dust level profile around the shearer at mine A , 

Improved shearer clearer external water spray system , 

Comparison of dust level profiles along the face at mines E and F , 

Dust level profiles along the face at mine E , 

Dust level profile around the shearer at mine F , 

Comparison of dust level profiles along the face, with and without sup- 
port movement on the intake, mine B , 

Dust level profile along the face at mine E , 

Dust level profile around the shearer at mine E , 

TABLES 

Dust source analysis , 

Cutting parameters and dust control procedures , 

Dust source analysis for mine A , 

Dust source analysis for mine B , 

Dust source analysis for mine C 

Dust source analysis for mine D 

Dust source analysis for mine E , 

Dust source analysis for mine F , 



4 
5 
6 
7 
7 
8 
9 
10 

11 
18 
19 



2 
11 
14 
15 
15 
16 
16 
17 





UNIT OF MEASUREMENT 


ABBREVIATIONS 


USED IN THIS REPORT 




f pm 


foot per minute 






mm 


millimeter 




ft 


foot 






pet 


percent 




gpm 


gallon per minute 






psig 


pound per square inch, 


gage 


h 


hour 






rpm 


revolution per minute 




in 


inch 






tps 


ton per shift 




mg/nr 5 


milligram per cubic 


meter 









DUST SOURCES AND CONTROLS ON THE SIX U.S. LONGWALL FACES 
HAVING THE MOST DIFFICULTY COMPLYING WITH DUST STANDARDS 

By Robert A. Jankowski 1 and John A, Organiscak 2 



ABSTRACT 

The Bureau of Mines has recently identified five major factors that 
contribute to high respirable dust levels on the six U.S. longwall 
faces having the most difficulty complying with Federal dust standards: 
(1) a poorly structured cutting sequence, (2) a poorly designed exter- 
nal water spray system, (3) marginal waterflow to the cutting drums, 
(4) minimal controls at the stage loader and crusher, and (5) the lack 
of effective controls for dust generated during support advance. The 
results of this survey illustrate the need to address all the major 
sources of longwall dust generation and the need for mine operators to 
implement a variety of control procedures to assure compliance. The 
Bureau of Mines will continue to assist mine operators in implementing 
improved dust controls and will work to identify and evaluate controls 
for dust generated during support advance. 



'Supervisory physical scientist. 
^Mining engineer. 
Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 



INTRODUCTION 



The Bureau of Mines has recently com- 
pleted a survey of the six U.S. longwall 
operations having the most difficulty 
complying with the Federal dust standard. 
Initially, 10 mines were identified, 
based on MSHA compliance records ; how- 
ever, during the course of this study, 4 
of these mines implemented improved dust 
controls, and although they were included 
in the survey, they are not discussed in 
this report. Thus, this survey repre- 
sents the problem areas identified on the 
six U.S. longwalls having the greatest 
difficulty complying with Federal dust 
standards. The objectives of the survey 
were to (1) identify the major dust 
sources encountered on these operations, 
(2) determine whether existing technology 
was capable of controlling dust from the 
major sources, and (3) identify the areas 
where existing technology was not ade- 
quate. This information would permit 
mine operators to select the most appro- 
priate control technique for a given dust 



source and provide additional direction 
to research efforts designed to develop 
control technology for specific problem 
areas. 

As each of the mines surveyed had a 
record of consistent difficulty complying 
with the Federal dust standard, all sam- 
pling was "short-term," often less than 
30 min. Two types of sampling were per- 
formed: Short-term gravimetric (_1) ,3 to 
identify and rank the major dust sources; 
and instantaneous (2) , using a Real-Time 
Aerosol Monitor (RAM) instrument devel- 
oped by the Bureau of Mines (3) , to eval- 
uate the effectiveness of existing dust 
control techniques. In addition to moni- 
toring dust levels, face airflow and wa- 
ter usage were measured throughout the 
shift. Operational parameters, such as 
cutting sequence, support advance, and 
mining practices, were studied to estab- 
lish their impact on dust generation and 
control. 



IDENTIFICATION OF DUST SOURCES 



Short-term gravimetric sampling was 
used to identify and rank the dust 
sources encountered on the six longwall 
operations surveyed. Details of this 
sampling procedure and dust source analy- 
sis can be found in appendix A. Five 
primary dust sources were identified (ta- 
ble 1) and were common to all longwall 
faces surveyed. They are intake dust, 
dust generated by coal transport and the 
stage loader, dust generated during move- 
ment of the roof supports, dust generated 



by the shearer during the cut pass, and 
dust generated by the shearer during the 
cleanup pass. Although initially it 
would appear that the last two causes 
could be combined as dust generated by 
the shearer, further studies indicate 
that both the source of generation and 

^underlined numbers in parentheses re- 
fer to items in the list of references 
preceding the appendixes at the end of 
this report. 



TABLE 1. - Dust source analysis, percent 



Dust source 



Mine A Mine B Mine C Mine D Mine E Mine F 



Intake , 

Stage loader-coal transport, 
Support movement 

Shearer: 

Head-to-tail cut pass.... 
Head-to-tail cleanup pass, 
Tail-to-head cut pass.... 
Tail-to-head cleanup pass, 



1 
25 
10 

60 

NAp 

NAp 

4 



5 
57 
31 

'0 

NAp 

NAp 

7 



5 
19 

1 

28 
NAp 

47 
NAp 



5 
20.5 
1 

53 
NAp 
NAp 

20.5 



9 

64 


NAp 
15 
12 

NAp 



8 

13 
29 

NAp 

50 



NAp 



NAp Not applicable. 

'Dust level at shearer was attributed to support dust, 



the applicable control technology are 
different and distinct. Dust generated 
during the cut pass is produced by the 
cutting action of the shearer drums , 
while dust generated during cleanup is 
produced during loading of cut material 
and trimming of bottom rock. 

At four of the six operations surveyed, 
the major source of dust was the shearer 
during the cut pass. The contribution 
ranged from 47 to 60 pet of the total 
respirable dust exposures of the longwall 
shearer operators. At mine D (table 1) , 
dust generated by the shearer during the 
cleanup pass was also a significant fac- 
tor, contributing 20.5 pet of the shearer 
operators' respirable dust exposures. 
This illustrates the need for adequate 
controls during the cleanup pass and 
shows that loading dry coal or trimming 
bottom rock can significantly increase 
shearer operators' respirable dust 
exposures. 

Dust generated by the stage loader-coal 
transport was the major source at mines B 
and E, contributing 57 and 64 pet of the 
shearer operators' dust exposures, re- 
spectively. At two additional opera- 
tions, mines A and D, dust from this 
source was significant, contributing 20 



to 25 pet of the shearer operators' dust 
exposures. This illustrates the need to 
address all primary sources of dust on a 
given longwall face. Depending on the 
particular operation, additional controls 
on the shearer may not have much effect 
on dust levels at the operator's posi- 
tion, since the source of exposure is not 
the shearer. 

Dust generated by movement of roof sup- 
ports can be a primary source at certain 
longwall faces. At mine B, 31 pet of the 
shearer operators' dust exposures was due 
to dust generated during support advance. 
Although not the major source, 29 pet of 
the respirable dust at mine F was gener- 
ated during movement of the roof sup- 
ports. Without an adequate dust source 
analysis, the mine operator is unable to 
reliably target the specific area to ad- 
dress when implementing improved dust 
control technology, and thus dedicated 
efforts may prove useless for reducing 
dust levels on any particular longwall 
face. Although in most instances the 
shearer is the primary dust source, and 
the major control efforts should be di- 
rected toward this area, coal transport- 
stage loader systems and movement of roof 
supports must not be overlooked. 



EFFECTIVENESS OF EXISTING CONTROLS 



One of the simplest and most effective 
methods to evaluate the effectiveness of 
a given dust control technique uses in- 
stantaneous dust monitors such as the 
RAM-I. Details of the sampling procedure 
are given in appendix B. These proce- 
dures can be used to evaluate the effects 
of cutting direction, external water 
spray systems, method of support advance, 
and techniques for controlling sources 
upwind of the longwall shearer. 

CUTTING SEQUENCE DESIGN 



the cutting action of the shearer drum, 
and the dust exposure of the shearer 
operator is usually determined by his po- 
sition relative to the lead drum, which 
is normally in the raised position, tak- 
ing a full sump. Thus, on longwall faces 
where the cut pass is taken from tail to 
head, against the primary airflow, or on 
bidirectional longwall faces , the shearer 
operator must remain at the controls on 
the return-air side of the primary dust 
source in order to maintain proper hori- 
zon control. 



At several of the operations surveyed, 
an important factor contributing to high 
levels of respirable dust at the shearer 
operators' work locations was the design 
of the cutting sequence. The primary 
source of dust produced by the shearer is 



To illustrate the effects of cutting 
sequence designs, dust profiles were con- 
structed from data collected at mines D 
and F (fig. 1). At mine D, the cut pass 
was from head to tail, placing the lead 
drum (the one generating the greatest 



LlI 
> 
UJ 



Q E 

co 3 

SI 
uj ^ 

z 

z 

CO 



12 



10 







Mine F, tail-to-head cut 

(lead drum upwind) 




1 



Increase in dust level 
due to change in cut 
direction 

Mine D, head-to-tail cut 

(lead drum downwind) 



1 



30 20 
Intake 



10 



Shearer 



10 20 30 
Return 



DISTANCE, ft 



FIGURE 1. - Comparison of dust level profiles around the shearer at mines D and F^ showing the ef= 
feet of cutting sequence and location of lead drum. 



amount of dust) on the return-air side of 
both shearer operators. At mine F, the 
cut pass was from tail to head, with the 
shearer operators downwind of the lead 
drum. At the three mines surveyed where 
the cut pass was taken tail to head, no 
special precautions or control techniques 
were taken to protect the shearer opera- 
tors from the high dust levels generated 
by the lead drum. It is imperative that 
mine operators examine their cutting se- 
quence and implement proper mining prac- 
tices to allow face workers to remain up- 
wind of the lead drum during most of the 
mining cycle. Optimum cutting sequences 
and mining cycles have been identified 
for both unidirectional (*\) and bidirec- 
tional (5) operations. These methods of 



operation can significantly reduce 
shearer operators' respirable dust expo- 
sures, thus helping mine operators com- 
ply with the dust standard while still 
maintaining adequate levels of shift 
production. 

EXTERNAL WATER SPRAY SYSTEM 

Simply keeping the shearer operators on 
the intake-air side of the lead drum will 
not insure lower dust exposures. The de- 
sign of the external water spray system 
has a significant effect on how quickly 
the dust generated by the cutting drums 
spreads out into the walkway and over the 
shearer operators. Without an external 
spray system, the dust follows the 



airflow patterns of the primary face air- 
flow. Physical obstructions such as the 
end of the machine body and drum cowls 
divert the primary airflow into the walk- 
way, around the machine. As the airflow 
moves into the walkway it picks up the 
dust generated by the cutting drums, in- 
creasing the shearer operators' dust 
exposure. 

This situation can actually be com- 
pounded by an external spray system ori- 
ented against the primary airflow. In 
the past, external spray systems have 
been mounted on the shearer body and ori- 
ented towards the cutting drums, in an 
effort to provide more water to the cut- 
ting zone. However, each spray acts like 
a small fan, moving air in the direction 
of the spray orientation. Sprays mounted 
on the machine body and oriented towards 
the intake-air side drum cause the dust 



to "boil" upwind against the primary in- 
take. This dust is then carried out into 
the walkway upwind of the shearer, and 
down over the shearer operators. The Bu- 
reau of Mines has developed and evaluated 
an optimum external spray system, the 
shearer clearer (6^) , which orients the 
sprays downwind and towards the face. 
This system uses the air-moving features 
of water sprays to confine the dust to 
the face area and set up a clean-air 
split in the walkway, over both shearer 
operators. 

Only two of the mines surveyed had at- 
tempted to apply the shearer clearer con- 
cept. Mine B had installed a shearer 
clearer system, but although the system 
was very effective for controlling 
shearer dust, this was not the major dust 
source on this operation (fig. 2). Mine 
E had also attempted to employ the 



UJ 

> 
LU 



10 



8 



CO 




30 20 
Intake 







l_[ 



Dust level attributed 
to support movement 



1 



Shearer 



DISTANCE, ft 



10 20 30 
Return 



FIGURE 2. - Dust level profile around the shearer at mine B, showing the effectiveness of external 
water sprays for controlling shearer dust. Note: Dust levels decrease until reaching the taildrum 
shearer operator. 



shearer clearer concept; however, the 
pressure on the intake-air side sprays 
exceeded 300 psig, and the airflow in- 
duced by this high pressure caused the 
dust to spread quickly out into the walk- 
way (fig. 3). The remaining mines either 
had an external spray system designed to 
provide additional water to the cutting 
zone or made no effort to use external 
sprays to help control dust. Figure 4 
shows the dust profile around the shearer 
at mine A. This system was typical of 
the designs used to provide additional 
water to the cutting zone. The intake- 
air side sprays were oriented upwind and 
caused the dust to boil 10 to 15 ft up- 
wind, and out into the walkway, over the 
shearer operators. 

Since the major dust source at four of 
the six operations surveyed was the cut- 
ting action of the shearer drums, the in- 
stallation of a shearer clearer system 



(fig. 5) should help to reduce the dust 
levels in the walkway adjacent to the 
shearer and lower shearer operators' res- 
pirable dust exposures. Note that figure 
5 shows an improved design of the origi- 
nal system, which not only uses less wa- 
ter but has been optimized to hold the 
dust against the face for a distance of 
35 to 40 ft downwind of the shearer. 
Operating pressure of the system is 
critical and should typically be main- 
tained between 100 and 150 psig at the 
nozzle. 

SHEARER WATER SUPPLY 

Although there are no specific guide- 
lines for water usage on longwall shearer 
sections, an earlier Bureau of Mines 
study (_7) has shown that longwalls that 
can consistently maintain compliance with 
Federal dust standards supply large vol- 
umes of water (>65 gpm) , primarily to the 







T 




•Increase in dust level 
from boi lout of upwind 
drum 



30 20 
Intake 







nn 



Shearer 



DISTANCE, ft 



10 20 30 

Return 



FIGURE 3. - Dust level profile around the shearer at mine E # showing the effects of high water 
pressure causing dust to boil upwind and into the walkway. 




30 20 
Intake 



Increase in dust level 
from boilout of upwind 
drum 



Shearer 



DISTANCE, ft 



20 30 
Return 



FIGURE 4, - Dust level profile around the shearer at mine A, showing the effects of spray orientation causing 
the dust to boil upwind and into the walkway. Note: Dust levels begin to increase 15 ft upwind of the shearer. 



LEGEND 
Dusty air 



♦ — Clean air 



Tail drum 



y^^ N 



2&L 



Head drum 



uv 



Operator 



Operator 



Direction of cut 
> 

Direction of airflow 



FIGURE 5, - Improved shearer clearer external water spray system. 



cutting drums. The average waterflow on 
the six longwall operations surveyed in 
this study was approximately 60 gpm; how- 
ever, this is misleading. On the long- 
wall faces where the shearer was the ma- 
jor dust source, the average waterflow to 
both drums was only 28 gpm. At mines D 
and F, the waterflow to the drums was 
less than 20 gpm. The effects of these 
low flows can be seen in figure 6. The 
waterflows to the shearer at mines E and 
F were both greater than 100 gpm; how- 
ever, the drum flows were approximately 
60 and 20 gpm, respectively. The instan- 
taneous dust level at the midpoint of the 
shearer averaged 4.2 mg/m 3 at mine E; at 
mine F the level was 8.6 mg/m 3 . 

Higher waterflows to the shearer drums 
not only reduce the dust generated during 
cutting, but also help to lower dust lev- 
els during face transport and in the 
beltlines. Since the majority of the wa- 
ter supplied to the drums is loaded out 



with the coal, problems resulting from 
water accumulating on the bottom are re- 
duced. The Bureau of Mines has identi- 
fied and documented an upgraded water 
supply system (8) that can significantly 
improve flow and pressure to the shearer. 

STAGE LOADER AND COAL TRANSPORT 

Most of the operations surveyed showed 
little concern for dust generated during 
coal transport and crushing operations at 
the stage loader. The contribution of 
these sources averaged 33 pet and ranged 
as high as 64 pet. The low waterflow to 
the shearer contributed significantly to 
these high dust levels , as did a lack of 
controls on the crusher at the stage 
loader. Figure 7 shows the face profiles 
from data collected at mine E. At this 
operation, the cut pass was from tail to 
head, and the waterflow to the shearer 
was approximately 100 gpm. This high 
flowrate was adequate to control dust 



14 



T 



T 



Mine F 







- 



Total flow 100 gpm 
Drum flow 60 gpm 

J I I 



1 



1 



1 



40 50 



60 



70 



10 20 30 
Headgate 

FACE LOCATION, support number 



80 90 
Tailgate 



FIGURE 6. - Comparison of dust level profiles along the face at mines E and F, showing the effects 
of high water flow to the cutting drums. 



> 

UJ 



8 



H 6 
^*> 

Q'E 

en 4 

o< 
war 



CO 



2 - 




5 ft on intake of shearer 



1 



1 



1 



1 



10 20 30 40 50 60 70 80 90 100 

Headgate Tailgate 

FACE LOCATION, support number 

FIGURE 7. - Dust level profile along the face at mine E, showing intake contamination due to dust 
generated by the crusher at the headgate. 



during coal transport, but not sufficient 
to control dust from secondary crushing 
operations at the stage loader. Starting 
at the tailgate, support 110, dust lev- 
els measured 15 ft on the intake of the 
shearer are relatively low and are due to 
coal transport. As the shearer cuts to- 
ward the headgate, dust levels on the 
intake-air side of the machine steadily 
increase as the transported material 
passes through the crusher at the head- 
gate. The dust level at the shearer is 
directly proportional to the dust level 
15 ft on the intake and is due to dust 
generated by the crusher at the headgate. 
Additional dust controls on the shearer 
would have minimal effect on the dust ex- 
posure of the shearer operators, and im- 
proved control technology must be applied 
to the major dust source, the stage 
loader. The Bureau of Mines has devel- 
oped improved dust controls for the stage 
loader (9) , which can reduce dust levels 
from this source by approximately 50 pet. 

SUPPORT DUST 

Most mine operators do not regard dust 
generated during support movement as a 
major problem, and there has been little 
work to develop technology to control 



dust from this source. Support dust was 
identified as a significant factor at 
mines B and F, and current technology is 
not adequate to control the dust from 
this source. Figure 8 shows the dust 
level profile around the shearer at mine 
F. The dust generated by the movement of 
roof supports significantly increased the 
intake-air dust levels approaching the 
shearer, thus increasing the dust expo- 
sure of both shearer operators. The ef- 
fects of dust from support movement can 
also be seen from figure 9. The average 
dust level at the midpoint of the shearer 
with support movement on the intake is 
8.7 mg/m 3 , while the dust level is only 
5.2 mg/m 3 when there is no support move- 
ment on the intake. 

Currently three procedures can be em- 
ployed to control dust generated during 
support movement. The simplest is to cut 
in the direction of face airflow and move 
the supports on the return air side of 
the shearer during the cleanup pass. 
This procedure does not control the dust 
but places the source on the return air 
side of all face workers. Roof condi- 
tions and clearance through the shearer 
underframe limit the application of this 
cutting cycle. 



10 



(/> 



LU 

> 
UJ 



if) 

Z> 

c/> 3 

Z>2 

o< 
ujq: 

-z. 

CO 



10 







-Support movement 




1 



30 20 
Intake 



10 



Shearer 



nu 



1 



10 20 30 
Return 



DISTANCE, ft 



FIGURE 8. - Dust level profile around the shearer at mine F, showing intake contamination due to 
dust generated by support movement. 



Several mine operators have installed 
water sprays on the roof support cano- 
pies, in an attempt to suppress the dust 
generated during support movement. Air- 
borne capture of respirable dust is dif- 
ficult, and the effectiveness of these 
sprays has not been adequately docu- 
mented. In addition, the application of 
water to the mine roof and floor can 
cause deterioration and ground control 
problems. 

One final procedure mine operators are 
employing in an effort to lower dust 
levels generated during support movement 



is to maintain a distance of at least 50 
ft between support advance and the 
shearer. This provides additional time 
for the primary face airflow to dilute 
and diffuse the dust before it reaches 
the shearer operators. Generally higher 
face airflows also help when employing 
this approach. The Bureau of Mines is 
conducting intensive in-house and con- 
tract (10) research to identify the fac- 
tors governing the generation of dust 
during support movement and the technol- 
ogy needed to control dust from this 
source. 



11 



UJ 
> 

LxJ 



CO 
O 

CO 

Z> 

o 

LxJ 
CO 



14 
12 h 

10 



I 8 

3 



< 6 

rr 



4 
2 



— i 1 r 

With 
support movement 




Without 
support movement 



10 20 30 40 50 60 70 80 90 

Headgate Tailgate 

FACE LOCATION, support number 

FIGURE 9. • Comparison of dust level profiles along the face, with and without support movement 
on the intake, mine B. 

TOTAL APPROACH REQUIRED 



Table 2 lists the cutting parameters 
and dust control procedures employed at 
the six U.S. longwalls faces having the 
greatest difficulty complying with the 
Federal dust standard. 



Previous Bureau of Mines research ( 11 ) 
has shown that slow-speed deep cutting 
can significantly reduce the amount of 
dust generated by the cutting drums. 
Five of the six mines surveyed had drum 



TABLE 2. - Cutting parameters and dust control procedures 













Average 


External 


Drum 








Cutting 


Tram 


Drum 


face 


water 


spray 


water 


spray 


Produc- 


Mine 


Cutting 
sequence 


height , 
in 


speed, 
f pm 


speed, 
rpm 


veloc- 
ity, 


system 1 


syst 


em 2 


tion, 




Flow, 


Pres- 


Flow, 


Pres- 


tps 












f pm 


gpm 


sure, 
psi 


gpm 


sure, 
psi 




A • • • 


Unidirectional 
head-to-tail. 


72- 84 


12 


45 


225 


20 


60 


25 


60 


800 


6 • • • 


•• *QO» • • • • • ••• 


108-116 


17 


45 


355 


20 


160 


30 


100 


1,500 


v-> * • • 


Bidirectional. 


78- 84 


12 


48 


400 








45 


60 


1,000 


D.. . 


Unidirectional 
head-to-tail. 


90- 96 


20 


28 


125 


15 


275 


20 


<15 


1,200 


E • . • 


Unidirectional 
tail-to-head. 


66- 84 


15 


60 


600 


40 


>300 


60 


>100 


1,500 


F... 


• • * QO • • • •« •• •• 


78- 84 


15 


37 


650 


80 


<15 


20 


<15 


1,800 



Upwind for mines A, E and F, 
2 Pick point for mines A and C 



shearer clearer for mine B; downwind for mine D. 
-F; cavity filling for mine B. 



12 



speeds less than 50 rpm, while one opera- 
tion (mine E) had seam conditions requir- 
ing 60 rpm to cut the coal. The average 
drum speed at the six operations surveyed 
was 44 rpm, which illustrates the indus- 
try's acceptance of this proven dust con- 
trol technique. However, as previously 
stated, no single control technique can 
insure low dust levels , and consideration 
must be given to a total approach, di- 
rected at all the dust sources on any 
given longwall face. 



airflow and production. No single con- 
clusion can be drawn from these parame- 
ters, as production ranged from 800 to 
1,800 tps and face airflow was 125 to 650 
fpm. The dust control techniques em- 
ployed at any given longwall operation 
should insure compliance with Federal 
standards while maintaining maximum pro- 
duction levels. If any area or source is 
overlooked, the dust standard may still 
be exceeded, even at minimal production 
levels and higher face airflows. 



Two additional parameters were also 
monitored during the survey — average face 



CONCLUSIONS 



Five major factors were identified that 
contributed to high dust levels on these 
operations: (1) A poorly defined or 
structured cutting sequence, which posi- 
tioned face workers on the return-air 
side of the lead cutting drum; (2) a 
poorly designed external water spray sys- 
tem, which allowed the dust produced by 
the shearer to boil upwind and be carried 
out into the walkway over the shearer 
operators; (3) marginal waterflow to the 
cutting drums , which permitted high lev- 
els of dust to become airborne during 
cutting and coal transport; (4) minimal 
controls at the stage loader and crusher, 
which caused immediate contamination of 
the primary intake; (5) the lack of ef- 
fective control technology for dust gen- 
erated during support movement. 



The results of this survey illustrate 
the need to address all the various 
sources of longwall dust generation. No 
one single control technique is adequate 
to maintain low dust levels , and the mine 
operator must implement a variety of con- 
trol procedures to assure compliance. 
Systems such as the Bureau of Mines 
shearer clearer, modified cutting se- 
quences , and an upgraded longwall water 
supply should help most longwall mine 
operators to lower face dust levels. 
However, the control technique must be 
appropriate for the dust source. The 
Bureau of Mines will continue to assist 
mine operators in implementing improved 
dust controls and to conduct research to 
identify and evaluate controls for dust 
generated during support advance. 



REFERENCES 



1. Page, S. J., R. A. Jankowski, and 
F. N. Kissell. How To Evaluate Longwall 
Dust Sources With Gravimetric Personal 
Samplers. BuMines IC 8894, 1982, 14 pp. 

2. U.S. Bureau of Mines. Instantane- 
ous Sampling Improved Longwall Dust Con- 
trol. Tech. News No. 134, Feb. 1982. 

3. . Improved Respirable Dust 

Monitor. Tech. News No. 72, Oct. 1979. 



4. 



Modified Cutting Sequence 



Exposures, 
1981. 



Tech. News No. 116, Nov. 



5. Jankowski, R. A., and J. Hetrick. 
Longwall Cuts Dust Buildup. Coal Age, v. 
87, No. 6, June 1982, 4 pp. 

6. Kissell, F. N. , N. Jayaraman, 
C. Taylor, and R. Jankowski. Reducing 
Dust at Longwall Shearers by Confining 
the Dust Cloud to the Face. BuMines TPR 
111, 1981, 21 pp. 



Reduces Longwall Shearer Operators' Dust 



13 



7. Taylor, C. D. , and R. A. Jankow- 
ski. How the Six Cleanest U.S. Longwalls 
Stay in Compliance. Min. Cong. J. , v. 
68, No. 5, 1982, 4 pp. 

8. U.S. Bureau of Mines. Upgrading 
Longwall Water Supply Systems To Reduce 
Dust. Tech. News No. 113, Oct. 1981. 



9. 



Stage Loader Dust Control 



Reduces Longwall Intake Contamination. 
Tech. News No. 156, Oct. 1982. 



10. Foster-Miller, Inc. Evaluate Fun- 
damental Approach to Longwall Dust Con- 
trol. Ongoing BuMines contract J0318097; 
for inf. , contact R. A. Jankowski, TPO, 
Pittsburgh Research Center, Pittsburgh, 
PA. 

11. U.S. Bureau of Mines. Deep Cut- 
ting Double Arm Shearer. Tech. News No. 
Ill, Oct. 1981. 



14 



APPENDIX A. —SAMPLING PROCEDURES AND DATA ANALYSIS 
FOR DUST SOURCE DETERMINATIONS 



The sampling is carried out by a team 
of two individuals, with each collecting 
mobile gravimetric samples during se- 
lected segments of the mining cycle. 
Sampling is divided into two main phases: 

1. A set of samples is collected on 
the head-to-tail pass (sampling locations 
B and C in the tables) . 

2. A set of samples is collected on 
the tail-to-head pass (sampling locations 
D and E in the tables). 

One individual stands at the midpoint 
of the shearer, and the other stands 



approximately 15 to 20 ft on the intake- 
air side of the shearer. They travel 
along the face, maintaining their respec- 
tive positions relative to the machine. 
In addition, there is a stationary sam- 
pler package located in the primary in- 
take to the longwall face, to measure the 
section intake dust concentration. It is 
important to emphasize that the dust con- 
centrations in the following tables rep- 
resent dust levels only during the actual 
cutting and cleanup operations and not an 
8-h time weighted average. As such, they 
can in no way be used for compliance 
purposes. 



TABLE A-l. - Dust source analysis for mine A 



Source 


Amount , 1 




Time 


fraction 


of 




Total, 


Percent 




mg/m 3 


X 


mining 


cycle, 


pet 


= 


mg/m 3 


of total 




0.1 (A) 


X 






100 




= 


0.1 


1 


Stage loader-conveyor 


2.4 (D-A) 


X 






100 




= 


2.4 


25 




1.6 (B-D) 


X 






65 




= 


1.0 


10 


Shearer (cleanup).... 


1.1 (E-D) 


X 






35 




= 


.4 


4 




9.0 (C-B) 


X 






65 




= 


5.9 


60 




NAp 








NAp 






9.8 


100 



NAp Not applicable. 

1 If an MRE equivalent is desired, multiply all concentrations 



Letters in parentheses key to the following explanations: 



Dus 



by 1.38. 
t level, 



mg/m- 



A — In primary intake 0.1 

B — 15 ft on intake of shearer head-to-tail pass (cutting) 4.1 

C — At midpoint of shearer head-to-tail pass (cutting).... 13.1 

D — 15 ft on intake of shearer tail-to-head pass (cleanup) 2.5 

E — At midpoint of shearer tail-to-head pass (cleanup).... 3.6 



15 



TABLE A-2. - Dust source analysis for mine B 



Source 


Amount, 1 Time fraction of Total, 
mg/m 3 X mining cycle, pet = mg/m 3 


Percent 
of total 




0.3 (A) X 100 = 0.3 
3.3 (D-A) X 100 = 3.3 
3.0 (B-D) X 60 1.8 
.9 (E-D) X 30 .4 
(C-B) X 60 =0 


5 




57 




31 




7 





NAp NAp 5.8 


100 



NAp Not applicable. 

1 If an MRE equivalent is desired, 



multiply all concentrations by 1.38. 
parentheses key to the following explanations: 

Dust level, 



Letters in 



mg/m J 

A — In primary intake 0.3 

B — 15 ft on intake of shearer head-to-tail pass (cutting) 6.6 

C — At midpoint of shearer head-to-tail pass (cutting).... 6.4 

D — 15 ft on intake of shearer tail-to-head pass (cleanup) 3.6 

E — At midpoint of shearer tail-to-head pass (cleanup).... 4.5 



TABLE A-3. - Dust source analysis for mine C 



Source 


Amount, 1 Time fraction of Total, 
mg/m 3 X mining cycle, pet = mg/m 3 


Percent 
of total 




0.2 (A) X 100 = 0.2 

.8 (D-A) X 100 = .8 

.1 (B-D) X 55 .05 

2.1 (C-B) X 55 1.2 

4.5 (E-D) X 45 2.0 


5 
19 




1 




28 

47 




NAp NAp 4.25 


100 



NAp Not applicable. 

1 1f an MRE equivalent is desired, 



multiply all concentrations by 1.38. 
parentheses key to the following explanations: 

Dust level, 



Letters in 



mg/m- 



A — In primary intake 0.2 

B — 15 ft on intake of shearer head-to-tail pass (cutting) 1.1 

C — At midpoint of shearer head-to-tail pass (cutting).... 3.2 

D — 15 ft on intake of shearer tail-to-head pass (cleanup) 1.0 

E — At midpoint of shearer tail-to-head pass (cleanup).... 5.5 



16 



TABLE A-4. - Dust source analysis for mine D 



Source 


Amount, 1 Time fraction of Total, 
mg/m 3 X mining cycle, pet = mg/m 3 


Percent 
of total 




0.3 (A) X 100 = 0.3 
1.2 (D-A) X 100 - 1.2 

.1 (B-D) X 65 .06 
3.5 (E-D) X 35 1.2 
4.7 (C-B) X 65 3.1 


5 

20.5 

1 




20.5 
53 




NAp NAp 5.86 


100 



NAp Not applicable. 

'if an MRE equivalent is desired, 



multiply all concentrations by 1.38. 
parentheses key to the following explanations: 

Dust level, 
mg/m 3 



Letters in 



A — In primary intake 0.3 

B — 15 ft on intake of shearer head-to-tail pass (cutting) 1.6 

C — At midpoint of shearer head-to-tail pass (cutting).... 6.3 

D — 15 ft on intake of shearer tail-to-head pass (cleanup) 1.5 

E — At midpoint of shearer tail-to-head pass (cleanup).... 5.0 



TABLE A-5. - Dust source analysis for mine E 



Source 


Amount, 1 Time fraction of Total, 
mg/m 3 X mining cycle, pet = mg/m 3 


Percent 
of total 




0.3 (A) X 100 = 0.3 

2.1 (D-A) X 100 = 2.1 

(B-D) X 45 =0 

.9 (C-B) X 45 .4 

.9 (E-D) X 55 .5 


9 
64 









12 
15 




NAp NAp 3.3 


100 



NAp Not applicable. 

1 If an MRE equivalent is desired, multiply all concentrations by 1.38. Letters in 
parentheses key to the following explanations: 

Dust level, 
mg/m 3 



A — In primary intake 0.3 

B — 15 ft on intake of shearer head-to-tail pass (cutting) 1.9 

C — At midpoint of shearer head-to-tail pass (cutting).... 2.8 

D — 15 ft on intake of shearer tail-to-head pass (cleanup) 2.4 

E — At midpoint of shearer tail-to-head pass (cleanup).... 3.3 



TABLE A-6. - Dust source analysis for mine F 



17 



Source 


Amount, 1 Time fraction of Total, 
mg/m 3 X mining cycle, pet = mg/m 3 


Percent 
of total 




0.6 (A) X 100 = 0.6 

1.0 (D-A) X 100 = 1.0 
5.2 (B-D) X 45 2.3 
(C-B) X 45 =0 

7.1 (E-D) X 55 3.9 


8 
13 




29 





50 




NAp NAp 7 . 8 


100 



NAp Not applicable. 

'if an MRE equivalent is desired, multiply all concentrations by 1.38. Letters in 
parentheses key to the following explanations: 

Dust level, 
mg/m 3 



A — In primary intake 0.6 

B — 15 ft on intake of shearer head-to-tail pass (cutting) 6.8 

C — At midpoint of shearer head-to-tail pass (cutting).... 6.7 

D — 15 ft on intake of shearer tail-to-head pass (cleanup) 1.6 

E — At midpoint of shearer tail-to-head pass (cleanup).... 8.7 



18 



APPENDIX B.— SAMPLING PROCEDURES FOR EVALUATING DUST CONTROL 
EFFECTIVENESS USING INSTANTANEOUS INSTRUMENTS 



The instantaneous dust-sampling instru- 
ments used during the surveys were GCA- 
RAM light-scattering instruments equipped 
with 10-mm nylon cyclones. These instru- 
ments were durable enough for underground 
use and light enough to be carried along 
the longwall face. Dust concentrations 
were read directly and recorded immedi- 
ately using handheld voice recorders. 
Face location, shearer location, spray 
orientation, support movement, etc., were 
also recorded and later transcribed into 
hard copy on the surface at the end of 
the survey. 

Sampling locations for these surveys 
were selected to obtain the following 
information: 

1. Dust levels on the upwind side of 
the shearer . It is important to measure 
dust levels at a location that is far 
enough upwind so as not to be affected by 
dust from the shearer, yet close enough 
to be representative of dust levels gen- 
erated by all sources upwind of the 
shearer. Without this information, it is 
often impossible to determine if changes 
in dust levels at the shearer are due to 
the control technology being evaluated or 
to dust sources upwind of the shearer. 
For this purpose, one instantaneous sam- 
pling instrument was carried at a con- 
stant distance (15 ft) on the upwind air 
side of the shearer. Sampling readings 
were taken approximately every 15 ft 
(three supports). 

2. Dust levels at the work location of 
the shearer operator . A dust control 
technique is designed to reduce the dust 
exposure of one or more mine workers. 
Sampling near the worker whose exposure 
is most directly affected by the dust 
source is usually the best method to 
evaluate the effectiveness of a dust con- 
trol technique. For this purpose, a sec- 
ond sampling instrument was carried at 
the midpoint of the shearer, less than 10 
ft from the shearer operators. Sampling 



readings were taken approximately every 
15 ft (three supports). 

3. Dust levels at the location where 
the control technology is designed to re- 
duce dust . As noted above, dust control 
procedures are normally designed to re- 
duce dust levels at locations where per- 
sonnel work. However, the effectiveness 
of a dust control technique is often dif- 
ficult to evaluate solely with respect to 
a selected work location because a work 
location can vary between operations and 
workers. Sampling results from areas 
around the dust source and selected work 
locations are needed to provide informa- 
tion about the extent of dust reduction 
resulting from the use of a control tech- 
nique. For this purpose, a third sam- 
pling instrument was used at a stationary 
location along the longwall face. As the 
shearer approached and passed this loca- 
tion, dust concentrations were recorded 
at 5-ft intervals from 25 ft on the in- 
take to an equal distance on the return- 
air side of the shearer. 

Figure B-l shows the face profiles from 
the data collected at mine E. In order 
to separate and evaluate the control pro- 
cedures used to reduce dust from coal 
transport and the stage loader, the tail- 
to-head cut pass data were plotted on the 
same graph. Starting at the tailgate, 
support 110, the dust level 15 ft on the 



32 

o< 
wrr 



2 - 



Midpoint of shearer 




N5 ft on intake of shearer 

J I I I L 



10 

Headgate 



20 



80 



90 100 
Tailgate 



30 40 50 60 70 

FACE LOCATION, support number 

FIGURE B-l, - Dust level profile along the face at 
mine E, showing the effectiveness ofcontrols fordust 
generated at the shearer and stage loader. 



19 



intake-air side of the shearer remains 
low until the coal is transported to the 
headgate. Dust generated by the crusher 
at the headgate significantly increases 
the dust level on the intake-air side of 
the shearer, thus increasing dust levels 
at the shearer midpoint. As the shearer 
approaches the headgate, there is a con- 
stant increase in coal going through the 
crusher, and corresponding increases in 
dust levels measured on the intake and at 
the midpoint of the shearer. These data 
show that the controls used to suppress 
dust during coal transport are relatively 
effective but that additional controls 
are needed to control dust generated by 
the crusher at the stage loader. 

Continuing with mine E, figure B-2 
shows the dust level profile around the 
shearer for a stationary location along 
the face. Although the mine had oriented 
the external spray system on the shearer 



downwind, the excessive water pressure 
still caused the dust to boil upwind 10 
to 15 ft; it was then carried out into 
the walkway over the shearer operators. 



30 20 
Intake 




-Increase in dust level 
from boilout of upwind 
drum 



10 



I I 



J_ 



I Shearer I 
DISTANCE, ft 



10 



20 30 
Return 



FIGURE B-2 t - Dust level profile around the shearer 
at mine E, showing the effectiveness of the external 
water spray system for controlling shearer dust. 



INT.-BU.O F MINES, PGH..P A. 27202 



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